The problem is there isn't much to vet, a lot of refugees live in poor conditions and don't have the luxury of technology like we do, a lot of them for the most part are off the grid and there isn't really anyway to do a proper check on them.
With U.S sending in troops to fight at Mosul, Iraq. You'll effectively be partially responsible for displacing over one million people so Ven is right in the fact you should own up to your interference in the Middle-East and help them outside of just going in guns blazing in their cities.
If you want to turn a blind eye on them then just stop involving your selves in their country.
Recently in Canada we accepted over 10,000 Syrian refugees and have and plan on accepting a lot more and we have had 0 terrorism attempts here.
Even if someone came to America as a non-terrorist, all the racism and hate towards them can easily make them dislike you guys because so many Americans dislike them.
But I do hate how entitled some of them feel in Canada, we are no longer allowed to say Merry Christmas in a public manner and stores can not have Merry Christmas on display anymore because it doesn't fit THEIR culture when they are in OUR country but it's mainly because our PM is a feminist/SJW (as he's stated himself).
There was a few hundred refugees in my town because I live beside the largest military base in Canada (where we had them stay) and they were all really nice people and no terrorist attempts when they could of easily hit us in our most important base.